CVE-2026-82883 in Login With Ajax Plugin
Summary
by MITRE • 09/02/2026
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in Marcus Login With Ajax allows Reflected XSS.
This issue affects Login With Ajax: from n/a through 4.5.1.
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Analysis
by VulDB Data Team • 09/02/2026
The identified security flaw represents a classic instance of improper neutralization of input during web page generation, commonly categorized under the Cross-Site Scripting (XSS) vulnerability class. Specifically, this is a reflected XSS attack vector located within the Marcus Login With Ajax plugin for WordPress. The vulnerability exists in versions ranging from no specific lower bound up through version 4.5.1. In a typical reflected XSS scenario, malicious scripts are injected into legitimate web requests and then immediately returned to the user's browser without proper sanitization or encoding by the server-side application logic. This mechanism allows an attacker to execute arbitrary JavaScript code in the context of the victim’s session, effectively bypassing same-origin policies that normally isolate web applications from each other.
From a technical perspective, the root cause lies in the inadequate validation and escaping of user-supplied data before it is rendered back into the HTML response. When a user interacts with the login interface, particularly through AJAX-driven submissions or URL parameters associated with authentication attempts, the application fails to properly sanitize inputs such as usernames, passwords, or redirect URLs. If these inputs contain malicious script payloads, they are embedded directly into the DOM structure of the resulting page. Because modern browsers execute scripts contained within HTML elements unless explicitly escaped, this allows the injected code to run in the context of the target website’s domain. This is particularly dangerous because it leverages the trust that users and other web services place in the specific WordPress site hosting the vulnerable plugin.
The operational impact of this vulnerability is severe due to its potential for session hijacking and credential theft. An attacker can craft a malicious link containing the XSS payload, which might be distributed via phishing emails, social engineering tactics, or compromised websites. When an authenticated user clicks on this link while logged into their WordPress account, the browser executes the injected script. This script can perform various hostile actions, including stealing session cookies and authentication tokens, redirecting the user to a malicious site designed to mimic the login page for credential harvesting, or performing unauthorized administrative actions if the victim has elevated privileges such as administrator rights. The use of AJAX in this context does not mitigate the risk; rather, it may facilitate stealthier attacks by allowing data exfiltration without necessarily triggering obvious browser warnings associated with full-page navigations.
This vulnerability aligns closely with CWE-79, which defines Improper Neutralization of Input During Web Page Generation as Cross-site Scripting (XSS). Furthermore, in the context of the MITRE ATT&CK framework for enterprise security, this behavior maps to techniques such as Client-side Injection and potentially Account Manipulation or Credential Access depending on the specific payload executed. The reflected nature of the attack means that it requires user interaction, which influences its exploitability score but does not diminish its severity when targeting high-privilege accounts within a WordPress environment.
To mitigate this risk, immediate action is required to update the Marcus Login With Ajax plugin to a version later than 4.5.1 where these input handling flaws have been addressed by the developers. Until an updated version is available or if updating is not immediately feasible, administrators should implement strict Content Security Policy (CSP) headers that restrict the execution of inline scripts and limit sources from which JavaScript can be loaded. Additionally, deploying a Web Application Firewall (WAF) with rules specifically tuned to detect and block common XSS payloads in HTTP requests can provide an additional layer of defense. It is also critical for developers reviewing similar codebases to ensure that all user inputs are strictly validated against expected formats and encoded using appropriate context-specific encoding methods such as HTML entity encoding before being rendered into the DOM, thereby neutralizing any malicious intent embedded within the input data.